Documente existing -c option of awesome-menu

awesome-menu.1.txt

@@ -9,7 +9,7 @@ awesome-menu - awesome menu system
 SYNOPSIS
 --------
 
-awesome-menu [-e command] <title>
+awesome-menu [-c config] [-e command] <title>
 
 DESCRIPTION
 -----------
@@ -42,6 +42,8 @@ You can do things like that:
 
 OPTIONS
 -------
+-c config::
+    Use an alternate configuration file instead of $HOME/.awesomerc. 
 -e command::
     Command to execute. The result is appended to the end of this command (like xargs).
 <title>::

awesome-menu.c

@@ -109,7 +109,7 @@ static void __attribute__ ((noreturn))
 exit_help(int exit_code)
 {
     FILE *outfile = (exit_code == EXIT_SUCCESS) ? stdout : stderr;
-    fprintf(outfile, "Usage: %s [-e command] <message>\n",
+    fprintf(outfile, "Usage: %s [-c config] [-e command] <message>\n",
             PROGNAME);
     exit(exit_code);
 }